The digestive function of the intestine for carbohydrates will be studied with emphasis on the role of the intestinal disaccharidases. After obtaining highly purified preparations of the individual enzymes from rat intestine, radioactive amino-acid incorporation experiments will be carried out to determine the rate of synthesis and degradation of the enzymes in vivo. The regulation and control of an individual enzyme will then be evaluated by study of the effect of various metabolic inhibitors as well as by study of the effect of variation in carbohydrate content of the diet. Since some patients with lactase deficiency are missing not only a lactase but also another Beta-galactosidase that splits only synthetic substrates, experiments will be carried out to determine whether patients with lactose maldigestion possess one or more intestinal proteins having similar structure to these two Beta-galactosidases, as estimated by immunological specificity. These studies should result in a better understanding of normal control mechanisms of the digestive enzymes and of their alteration in pathological states.